With the increasing popularity of personal computers, handheld appliances and the like, there has been a corresponding increase in the popularity and affordability of image rendering/manipulation applications.
Thus, for example, many personal computers and workstations are being configured as multimedia devices that are capable of receiving image data, for example, directly from a digital camera or indirectly from another networked device. These so-called multimedia devices are further configured to display the image data (e.g., still images, video, etc.). As for still images and single video frames, most multimedia devices can be further coupled to a printing device that is configured to provide a printed hardcopy of the image data.
When provided with the appropriate software application(s), the multimedia device can be configured to allow the user to manipulate all or portions of the image data in some manner. For example, there is a variety of photo/drawing manipulation applications and video editing applications available today. One example of a photo/drawing manipulation program is PhotoDraw® 2000, available from the Microsoft Corporation of Redmond, Wash. Another example of an image manipulation program is Picture It! 2000, also available from the Microsoft Corporation. One example of a video editing application is Adobe Premiere 6.0 available from Adobe Systems Incorporated of San Jose, Calif.
These and other image manipulation programs provide a multitude of image editing tools/features. In some instances, for example, in the key-frame evaluation and photo quality estimation features of Picture It! 2000, the image manipulation program may need to calculate certain characteristics associated with the image data in terms of its' blurriness/sharpness. Doing so allows for the user and/or the application to selectively or automatically manipulate blurred image data in some desired fashion. For example, a blurred portion of the image may be sharpened or perhaps protected from additional blurring.
With this in mind, previous methods for calculating blur characteristics have been designed for image restoration. By way of example, see the article by M. C. Chiang and T. E. Boult, titled “Local Blur Estimation and Super-Resolution”, as published in Proc. IEEE Computer Society Conference on Computer Vision and Pattern Recognition, pp. 821-826, June 1997. Also, for example, see the article by R. L. Lagendijk, A. M. Tekalp and J. Biemond, titled “Maximum Likelihood Image and Blur Identification: A Unifying Approach” as published in Optical Engineering, 29(5):422-435, May 1990.
These exemplary conventional techniques utilize methods that estimate the parameters needed by the reverse process of blur. Unfortunately, these methods tend to be complex and time-consuming.
Still other techniques utilize compressed domain methods based on discrete cosine transform (DCT) coefficient statistics, which can be used to estimate the blurriness of motion picture expert group (MPEG) frame in real-time. For example, see the methods presented by Xavier Marichal, Wei-Ying Ma and HongJiang Zhang at the International Conference on Image Processing (ICIP) in Kobe, Japan on Oct. 25-29, 1999, as published in an article titled “Blur Determination in the Compressed Domain Using DCT Information”. Unfortunately, these methods often find it difficult to handle images with relatively large uni-color patches.
Hence, there is an on-going need for improved methods and apparatuses for calculating or otherwise determining blurriness/sharpness characteristics in an image.